Peter: There are several models available. I have used a Hitachi gear reduction model for over 8 years and had absolutely no problems. It is several pounds lighter has an integeral solenoid and because of its reduced size allows for more header clearance.
The first OEM use of this model as I recall was on a mid 70's Datsun 240/260 Z. The end plate and gear had to be changed. Tilton markets a very good one, the one in the middle this is the design I have. The pictures are for Chevy & Mopar application. There are other brands and some clones too. The one on the left is a Permanent Magnet style, the one on the right is for Ultra high compression (notice the longer brush plate area)
Tilton:
Mcleod:
http://www.mcleodind.com/cgi-bin/fcc...ostname=MCLEOD
Rick